Wireless communication is constantly increasing in the world today. Efficient usage of communication resources is a hot topic in any type of wireless communication network, such as different 3GPP defined access technology networks, e.g. Global System for Mobile Communication, GSM, High Speed Packet Access, HSPA and Long Term Evolution, LTE. For achieving efficient communication in such wireless communication networks, a good estimation of signal to noise ratio, SNR, over individual wireless connections is of interest. For example, with a good estimation of SNR, traffic resources of a base station can be allocated to different mobile stations connected to the base station so that the traffic resources of the base station are efficiently used.
One area where it is important to allocate traffic resources efficiently between mobile stations and a base station is when using a service called Transmission Time Interval, TTI, bundling for transmitting Voice over IP, VoIP, packets in LTE between a User Equipment, UE (the mobile station of LTE is called UE) and an eNodeB (the name of the base station in LTE). TTI bundling was standardized in 3GPP to provide more efficient uplink transmission of delay sensitive packets. With TTI bundling enabled the UE transmits the same VoIP packet in 4 consecutive TTIs, thereby reducing the delay, since no Hybrid Automatic Repeat Request, HARQ, feedback is required between the transmissions, and the header overhead, since no RLC segmentation is needed. On the other hand, when the pathloss is small and a VoIP packet can be transmitted within one TTI, the extra transmissions from TTI bundling is only waste. It is therefore needed to only enable TTI bundling for a user when it is needed. One effective method for this is described in WO2013112078 in which the Signal to Noise Ratio is measure for a UE and the UE is switched to TTI bundling when the SNR becomes too poor.
However, in WO2013112078 there is no difference made between disturbances from noise and disturbances from interference. Consequently, what is actually measured in WO2013113078 is Signal to Interference and Noise Ratio, SINR. TTI bundling is a good way to reduce latency when the pathloss is high, i.e. when the signal has degraded so that the difference between signal strength and ambient noise, SNR, is low. On the other hand, TTI bundling is not suitable for use when the interference is high, where interference signifies disturbances from signal sent from other nearby lying communication sources, like other UEs, other eNodeBs etc. The reason is that when the UE is not power limited, which is the case when the interference is high but the pathloss is low to moderate, larger packets can be scheduled by simply using more Physical Resource Blocks, PRBs, in a single TTI, which is much more efficient than using TTI bundling. But when TTI bundling is enabled, the number of PRBs is limited to 3, and therefore the throughput becomes severely limited also in a relatively unloaded cell with many unused PRBs. Also, a switching algorithm based on SINR can become unstable. If UEs are switched to TTI bundling due to high interference, the additional transmissions will further increase the interference level. This may, in turn, cause UEs in other cells to trigger TTI bundling. Consequently, there is a need for a better way to detect SNR for use in deciding whether to use TTI bundling or not for a UE in a wireless communication system.